What Are Clinical Trials?

Laura Dorwart
·8 min read
<p>Hinterhaus Productions / Getty Images</p>

Hinterhaus Productions / Getty Images

Medically reviewed by Steffini Stalos, DO

Clinical trials are research studies that test how to best prevent, screen for, diagnose, manage, and treat various health conditions. People who live with an underlying health condition or disease and volunteers who haven’t been diagnosed with any conditions can participate in these studies.

The results from clinical trials allow researchers and healthcare providers to understand how they can detect and treat a variety of health conditions, from cancer to chronic conditions like diabetes and heart disease. Your participation can provide important information about the safety and effectiveness of new treatments and health screening methods that scientists are developing.

Why Are Clinical Trials Important?

Before new medical interventions for diagnosing and treating diseases can be offered to the public, they go through a rigorous testing process to determine their safety and effectiveness. Clinical trials are a key step in the process of advancing medicine.

Experts conduct clinical trials to test the following:

  • Drugs

  • Drug combinations

  • Biological products (such as vaccines)

  • Medical devices

  • Surgical procedures

  • Ways to encourage health-promoting behaviors and implement interventions

  • Screening methods

  • Improvements to existing treatments

  • Methods of delivering healthcare services

  • How to improve the quality of life for people with chronic or terminal conditions

How Do Clinical Trials Work?

Initially, scientists will test a medical intervention through laboratory and/or animal studies. Once they complete that step, it’s time to test a new intervention or treatment in the human population.

Every clinical trial is led by a principal investigator (PI), who guides a team of experienced medical researchers through the process. Together with their team, the PI develops a detailed plan for the clinical trial—known as the "protocol." This plan includes:

  • The research question(s) that the experts are investigating

  • Eligibility criteria that determine who can participate in a clinical trial

  • Details about potential risks that participants might face and how to protect against these risks

  • The approximate length of the study

  • Information about the testing and treatment process (e.g., what the intervention aims to do)

Once a research team has completed their protocol, they submit and present their plan to the Institutional Review Board (IRB). This committee will review and approve the proposed protocol based on the potential benefits and risks of the study, and determine whether it is safe and ethical to conduct.

If and when a research team gains approval from the IRB, they can begin to conduct the clinical trial in phases. In each phase, researchers gather more data on how well a specific treatment works and how safe it is. Each phase can take anywhere from a few months to four years. From start to finish, a clinical trial can take 7-10 years, or sometimes more. After testing is complete, the research team licenses their medical intervention and markets their product for wider use.

Phases of a Clinical Trials

There are four distinct phases of a standard clinical trial. These include:

  • Phase I: The purpose of this phase is to gather more information about the safety and potential side effects associated with a new medical intervention. Then, researchers test the treatment among a group of 20-80 participants. These participants include people who have a diagnosis for the condition in question and those who don't.

  • Phase II: A larger group of people (typically up to 300) who have the condition in question tests the same intervention. This phase can take up to two years.

  • Phase III: Between 1,000 and 3,000 people with the condition take the drug or treatment to test its safety and effectiveness, as well as to compare it to similar interventions. This can take up to four years.

  • Phase IV: The drug undergoes further testing and monitoring in the general population after being approved by the U.S. Food and Drug Administration (FDA).

Who Can Participate?

Both children and adults can participate in clinical trials, depending on what the clinical trial is investigating. The people who participate in clinical research fall into one of two categories:

  • Healthy volunteers: These volunteers are those who haven’t been diagnosed with the condition in question. Generally, these people fall into the “control” group, which is the group that researchers use to compare the patient volunteers to.

  • Patient volunteers: People who live with the health condition that the researchers are investigating fall into this category. Some people in this group may benefit from the treatment directly, while others participate in the trial to learn more medical knowledge about their condition.

Researchers select clinical trial participants based on certain inclusion and exclusion criteria—or a set of rules that researchers create to include or exclude someone from participating in the trial. You may or may not qualify for a given clinical trial based on factors like:

  • Age

  • Assigned sex at birth

  • The medical diagnosis or condition you live with

  • The stage or severity of your condition

  • Additional health conditions that you might have

  • Your personal or family medical history

  • Treatments or medications you've previously used or are currently using

  • Lifestyle and behavioral factors

Benefits and Risks of Participating in Clinical Trials

People participate in clinical trials for many different reasons. Some potential benefits of participating in a clinical trial include:

  • Contributing to medical advancements

  • Expanding medical knowledge

  • Improving the lives of people who need medical treatment, both now and in the future

  • Getting top-notch medical care and attention from a highly qualified team of healthcare providers and researchers

  • Accessing new treatment options and medical devices

  • Benefiting from treatments that may be safer, have fewer side effects, or work more effectively than the currently available treatment options

Still, there are always potential side effects when participating in medical research. Some of the potential risks and downsides of taking part in a clinical trial include:

  • Adverse side effects from the treatment approach being tested

  • More frequent visits with healthcare providers

  • Traveling to the facility where the research is being conducted

  • Healthcare costs that may not be covered by your insurance

If you’re thinking about participating in a clinical trial, consider asking the following questions first:

  • What is this study trying to accomplish?

  • How was the study approved and funded?

  • What are the potential short and long-term benefits of the treatment?

  • What are the potential short and long-term risks of the treatment?

  • What steps are you taking to ensure the safety of study participants?

  • How will my response to the treatment be monitored?

  • How long will the study take to complete?

  • How will I find out about the results?

  • Will I receive the treatment after the clinical trial is over?

  • Are there other treatment options available?

What to Expect from a Clinical Trial

Before signing up for a clinical trial, you will go through the informed consent process. In this first step, the study organizers and researchers will inform you about the goals, logistics, and purpose of the trial, as well as educate you about the potential risks and side effects. You will also have the opportunity to ask questions and get more information.

If you’d like to participate in the clinical trial, you will then sign an informed consent form. It’s important to note that you can opt out of a clinical trial at any time—even if you’ve already agreed to participate—without any risks or penalties of any kind.

Once you sign the consent form, the researchers may screen (or, interview) you to ensure that you fit the study’s eligibility criteria. If you consent and are accepted into the study, your participation will begin with a preliminary visit with the medical team. You may have to undergo a physical and/or cognitive examination at this point—depending on what the clinical trial is about.

While undergoing the treatment, you will most likely visit with the research staff several times for medical testing and monitoring. You may have to report any side effects and symptoms to researchers along the way. This process could take several months or more.

After the clinical trial concludes, researchers will synthesize and analyze the data they collected during the study. They may also publish their results in a peer-reviewed medical journal or other publication. If you participate in a clinical trial, you can ask the research staff whether or not you will find out the findings of the study and where you can find the results if they do submit a paper to a journal.

How to Find a Clinical Trial

If you're interested in participating in a clinical trial, there are several different ways to find a trial and learn whether you are eligible. You may try:

A Quick Review

Participating in clinical trials allows you to play a pivotal role in advancing medical knowledge. If you’ve been diagnosed with a particular health condition, being a part of a clinical trial can also help you gain access to new treatments that scientists are developing. If you’re curious about participating in a clinical trial, talk to your healthcare provider about potential resources. You can also search for upcoming or ongoing trials online.

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